U.S. patent number 9,286,920 [Application Number 13/756,379] was granted by the patent office on 2016-03-15 for method for compensating for phase variations in an interferometric tapered waveguide in a heat assisted magnetic recording head.
This patent grant is currently assigned to Western Digital (Fremont), LLC. The grantee listed for this patent is Western Digital (Fremont), LLC. Invention is credited to Yufeng Hu, Ut Tran.
United States Patent |
9,286,920 |
Hu , et al. |
March 15, 2016 |
Method for compensating for phase variations in an interferometric
tapered waveguide in a heat assisted magnetic recording head
Abstract
A method fabricates an interferometric tapered waveguide (ITWG)
for a heat-assisted magnetic recording (HAMR) transducer. The ITWG
is defined from at least one waveguide layer. The waveguide
layer(s) include an energy sensitive core layer. The energy
sensitive core layer has an index of refraction that varies in
response to exposure to energy having a particular wavelength
range. The step of defining the ITWG includes defining a plurality
of arms for the ITWG. At least one phase difference between the
arms is determined. At least one of the arms is exposed to the
energy such that the index of refraction of the energy sensitive
core layer in the arm(s) is changed and such that the phase
difference(s) between the arms is changed.
Inventors: |
Hu; Yufeng (Fremont, CA),
Tran; Ut (San Jose, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Western Digital (Fremont), LLC |
Fremont |
CA |
US |
|
|
Assignee: |
Western Digital (Fremont), LLC
(Fremont, CA)
|
Family
ID: |
55450203 |
Appl.
No.: |
13/756,379 |
Filed: |
January 31, 2013 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B
6/122 (20130101); G02B 6/1228 (20130101); G11B
5/314 (20130101); G11B 5/6088 (20130101); G11B
5/3163 (20130101); G11B 7/1384 (20130101); G02B
6/125 (20130101); G11B 2005/0021 (20130101) |
Current International
Class: |
G11B
7/00 (20060101); G11B 7/22 (20060101); G11B
5/00 (20060101); G11B 5/31 (20060101); G11B
7/1384 (20120101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
1498878 |
|
Jan 2005 |
|
EP |
|
1501076 |
|
Jan 2005 |
|
EP |
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Other References
Chen-Fu Chu, et al., "Study of GaN light-emitting diodes fabricated
by laser lift-off technique", Journal of Appl. Phys., vol. 95, No.
8, Apr. 15, 2004, pp. 3916-3922. cited by applicant .
Chao-Yi Tai, et al., "UV Photosensitivity in a Ta2O5 Rib Waveguide
Mach-Zehnder Interferometer", IEEE Photonics Technology Letters,
vol. 16, No. 6, Jun. 2004, pp. 1522-1524. cited by applicant .
Chubing Peng, "Surface-plasmon resonance of a planar lollipop
near-field transducer", Applied Physics Letters 94, 171106 (2009),
3 pages. cited by applicant .
Wang, et al., ""Thermo-optic properties of sol-gel-fabricated
organic-inorganic hybridwaveguides"", J. Appl. Phys., vol. 94, No.
6, Sep. 15, 2003, pp. 4228-4230. cited by applicant.
|
Primary Examiner: Pendleton; Dionne H
Claims
We claim:
1. A method for providing an interferometric tapered waveguide
(ITWG) for a heat-assisted magnetic recording (HAMR) transducer
comprising: defining the ITWG from at least one waveguide layer,
the at least one waveguide layer including an energy sensitive core
layer, the energy sensitive core layer having an index of
refraction that varies in response to exposure to energy having a
particular wavelength range, the step of defining the ITWG
including defining a plurality of arms for the ITWG; determining at
least one phase difference between the plurality of arms; and
exposing at least one of the plurality of arms to the energy after
the determining step such that the index of refraction of the
energy sensitive core layer in the at least one of the plurality of
arms is changed and such that the at least one phase difference
between the plurality of arms is changed to at least one new phase
difference, the at least one new phase difference being
substantially constant during operation of the HAMR transducer and
in-operation of the HAMR transducer, wherein the HAMR transducer is
one of a plurality of HAMR transducers on a wafer and wherein the
step of exposing the at least one of the plurality of arms to the
energy is performed on a wafer level for the entire wafer.
2. The method of claim 1 further comprising: providing the at least
one waveguide layer.
3. The method of claim 1 further comprising: providing a mask on
the ITWG, the mask being opaque to the energy and including an
aperture therein, the aperture exposing a portion of the at least
one of the plurality of arms, covering a remaining portion of the
at least one of the plurality of arms, and covering any remaining
arms of the plurality of arms.
4. The method of claim 3 wherein the at least one waveguide layer
includes a top cladding layer, step of providing the mask further
including: providing the mask on the top cladding layer.
5. The method of claim 4 wherein the HAMR transducer further
includes an overcoat layer, the mask residing between the overcoat
layer and the top cladding layer.
6. The method of claim 4 wherein the HAMR transducer further
includes an overcoat layer, the overcoat layer residing between the
mask and the top cladding layer.
7. The method of claim 1 wherein the step of exposing the at least
one of the plurality of arms is performed on a device level.
8. The method of claim 1 wherein the ITWG has at least one target
phase difference, the at least one target phase difference being
constant, the at least one new phase difference being closer to the
at least one target phase difference than the at least one phase
difference.
9. The method of claim 1 wherein the HAMR transducer further
includes at least one grating corresponding to at least a portion
of the plurality of arms, the at least one grating contributing to
the phase difference.
10. The method of claim 9 wherein the step of exposing the at least
one of the plurality of arms further includes: exposing at least a
portion of the least one grating to the energy.
11. The method of claim 1 wherein the HAMR transducer further
includes at least one trench corresponding to at least a portion of
the plurality of arms, the at least one trench contributing to the
phase difference.
12. The method of claim 11 wherein the step of exposing the at
least one of the plurality of arms further includes: exposing at
least a portion of the at least one trench to the energy.
13. A method for providing an interferometric tapered waveguide
(ITWG) for a heat-assisted magnetic recording (HAMR) transducer
comprising: defining the ITWG from at least one waveguide layer,
the at least one waveguide layer including an energy sensitive core
layer, the energy sensitive core layer having an index of
refraction that varies in response to exposure to energy having a
particular wavelength range, the step of defining the ITWG
including defining a plurality of arms for the ITWG; determining at
least one phase difference between the plurality of arms; and
exposing at least one of the plurality of arms to the energy after
the determining step such that the index of refraction of the
energy sensitive core layer in the at least one of the plurality of
arms is changed and such that the at least one phase difference
between the plurality of arms is changed to at least one new phase
difference, the at least one new phase difference being
substantially constant during operation of the HAMR transducer and
in-operation of the HAMR transducer; wherein the plurality of arms
have a target phase difference, the target phase difference
corresponding to a target optical length for one of the plurality
of arms, and wherein the step of defining the ITWG further
includes: defining the one of the plurality of arms to have an
optical length greater than the target optical length such that the
at least one phase difference is greater than the target phase
difference; and wherein the index of refraction of the energy
sensitive core layer is reduced by exposure to the energy.
14. A method for providing an interferometric tapered waveguide
(ITWG) for a heat-assisted magnetic recording (HAMR) transducer
comprising: defining the ITWG from at least one waveguide layer,
the at least one waveguide layer including an enemy sensitive core
layer, the energy sensitive core layer having an index of
refraction that varies in response to exposure to energy having a
particular wavelength range, the step of defining the ITWG
including defining a plurality of arms for the ITWG; determining at
least one phase difference between the plurality of arms; and
exposing at least one of the plurality of arms to the enemy after
the determining step such that the index of refraction of the
energy sensitive core layer in the at least one of the plurality of
arms is changed and such that the at least one phase difference
between the plurality of arms is changed to at least one new phase
difference, the at least one new phase difference being
substantially constant during operation of the HAMR transducer and
in-operation of the HAMR transducer; wherein the plurality of arms
have a target phase difference, the target phase difference
corresponding to a target optical length for one of the plurality
of arms, and wherein the step of defining the ITWG further
includes: defining the one of the plurality of arms to have an
optical length less than the target optical length such that the at
least one phase difference is less than the target phase
difference; and wherein the index of refraction of the energy
sensitive core layer is increased by exposure to the energy.
15. A method for providing an interferometric tapered waveguide
(ITWG) for an energy-assisted magnetic recording (HAMR) transducer,
the method comprising: providing a bottom cladding layer; providing
an energy sensitive core layer on the bottom cladding layer, the
energy sensitive core layer having an index of refraction that
decreases in response to exposure to energy having a particular
wavelength range; providing a top cladding layer on the energy
sensitive core layer; defining the ITWG including defining a
plurality of arms for the ITWG, the ITWG having a target phase
difference, the target phase difference corresponding to a target
optical length for an arm of the plurality of arms, the arm of the
plurality of arms having a longer optical length greater than the
optical length such that the phase difference is greater than the
target phase difference; providing a mask on the plurality of arms,
the mask being opaque to the energy and including an aperture
therein, the aperture exposing a portion of the arm, covering a
remaining portion of the arm, and covering any remaining arms of
the plurality of arms; determining at least one phase difference
between the arm and the any remaining arms; and exposing the
portion of the arm to the energy after the determining step such
that the index of refraction of the energy sensitive core layer in
the portion of the arm is reduced and such that the least one phase
difference between the arm and the any remaining arms is changed to
at least one new phase difference, the at least one new phase
difference being substantially constant during operation of the
HAMR transducer and in-operation of the HAMR transducer.
16. The method of claim 15 wherein the HAMR transducer further
includes an overcoat layer, the mask residing between the overcoat
layer and the top cladding layer.
17. The method of claim 15 wherein the HAMR transducer further
includes an overcoat layer, the overcoat layer residing between the
mask and the top cladding layer.
18. The method of claim 15 wherein the ITWG has at least one target
phase difference, the at least one target phase difference being
constant, the at least one new phase difference being closer to the
at least one target phase difference than the at least one phase
difference.
Description
BACKGROUND
FIGS. 1-2 depict plan and side views, respectively, of a portion of
a conventional heat assisted magnetic recording (HAMR) transducer
10. The HAMR transducer 10 includes a pole (not shown), coil(s)
(not shown), and other components used in writing to a media (not
shown). The HAMR transducer 10 is coupled to a laser (not shown)
for providing light energy to the HAMR transducer 10. In addition,
the HAMR transducer includes a conventional interferometric tapered
waveguide (ITWG) 60 for directing light from the laser to a near
field transducer (NFT) near the ABS. The conventional ITWG 20
includes a bottom cladding layer 12, a core layer 14, and a top
cladding layer 16. The core layer 14 is formed into arms 22 and 24
as well as tapered portion 26. In operation, light is coupled into
the ITWG 20 and confined to a smaller mode in tapered region 26.
The light is split into the arms 22 and 24. This is typically
accomplished using a Y-splitter, as shown in FIG. 1, or a multimode
interferometric (MMI) device.
At the ABS, light from the arms 22 and 24 of the ITWG 20 is out of
phase. Each arm 22 and 24 is designed to have a different optical
length. The differing optical lengths are due to differences in
length, thickness and width of the arms 22 and 24. The arms 22 and
24 of the conventional ITWG 20 thus have an optical path
difference. When the light from the arms 22 and 24 converges near
the ABS, the light from the arm 22 is out of phase from the light
from the arm 24 because of this optical path difference. Thus, the
arms 22 and 24 have a phase difference. The target phase difference
is the desired phase difference between light from the arms 22 and
24 at or near the ABS, for example at the NFT (not shown).
In operation, the conventional ITWG 20 directs light energy from
the laser to the NFT (not shown). Light from the arms 22 and 24
having the target phase difference provides a desired interference
pattern at the NFT. For example, for some HAMR transducers 10, the
target phase difference is 180.degree.. The NFT converts the
electromagnetic energy in the interference pattern into surface
plasmons at the NFT. The NFT then transfer this energy to a highly
localized field, and thus a small spot, at the media. The
conventional HAMR head 10 may then use the heat at and/or around
the spot to magnetically write to the media.
FIG. 3 depicts a conventional method 50 for forming the
conventional ITWG 20. The bottom cladding layer 12, core layer 14
and top cladding layer 16 are deposited, via step 52. The ITWG
pattern is then transferred to the waveguide layers 12, 14 and 16,
via step 54. Typically, a mask that covers the arms 22 and 24, the
tapered portion 26 and any remaining portions of the ITWG 20 is
provided. The exposed portions of the top cladding layer 16 and
core layer 14 are removed. A portion of the bottom cladding layer
12 might also be removed, for example by over etching the core
layer 14. A trench is thus formed in the top cladding layer 16 and
core layer 14. The ITWG 20 is thus defined. The areas surrounding
the ITWG are refilled with a dielectric 18, via step 56. The top
cladding 16, dielectric 18 and bottom cladding 12 layers may be
formed of the same material. Thus, the boundaries between the
layers 12, 16 and 18 are denoted by dashed lines and the dielectric
18 may be considered part of the top cladding layer 16. The ITWG 20
may thus be formed.
Although the conventional ITWG 20 and method 10 function, there are
drawbacks. In particular, efficiency of the NFT may not be
sufficient for operation of the conventional HAMR transducer 10.
The ability of the NFT to adequately perform its functions depends
upon a number of factors. The NFT parameters, such as the NFT
shape, size and materials, influence NFT performance. Illumination
parameters related to the energy input from the laser and directed
by the ITWG 20 also affect NFT performance. The phase difference of
the light arriving at the NFT from the arms 22 and 24 is one such
parameter. Processing limitations may result in variations in the
thickness, width, length, and/or to certain extent the refractive
index of the conventional ITWG 20. Variations in the
NFT-to-waveguide overlay and voids in the conventional ITWG 20 may
also affect the optical path length and thus phase difference
between the arms 22 and 24. Further, the laser diode wavelength and
temperature variations of the conventional transducer 10 may also
affect the phase difference between the arms 22 and 24. The ability
of the conventional ITWG 20 to provide light having the target
phase difference at the NFT may be adversely affected. If the light
from the arms 22 and 24 does not have the target phase difference,
the desired interference pattern may be shifted off of the NFT.
Performance of the NFT and, therefore, the conventional HAMR
transducer 10 may thus be hindered.
Accordingly, what is needed is an improved method for fabricating
an ITWG in a HAMR transducer.
SUMMARY
A method fabricates an interferometric tapered waveguide (ITWG) for
a heat-assisted magnetic recording (HAMR) transducer. The ITWG is
defined from at least one waveguide layer. The waveguide layer(s)
include an energy sensitive core layer. The energy sensitive core
layer has an index of refraction that varies in response to
exposure to energy having a particular wavelength range. The step
of defining the ITWG includes defining a plurality of arms for the
ITWG. At least one phase difference between the arms is determined.
At least one of the arms is exposed to the energy such that the
index of refraction of the energy sensitive core layer in the
arm(s) is changed and such that the phase difference(s) between the
arms is changed.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
FIGS. 1-2 are diagrams depicting plan and side views of a
conventional waveguide in a conventional magnetic transducer.
FIG. 3 is a flow chart depicting a conventional method for
fabricating a side shield.
FIG. 4 is a flow chart depicting an exemplary embodiment of a
method for fabricating an interferometric tapered waveguide for a
magnetic recording transducer.
FIG. 5 is a diagram depicting a disk drive including a heat
assisted magnetic recording transducer.
FIGS. 6-7 are diagrams depicting plan and side view an exemplary
embodiment a heat assisted magnetic recording transducer.
FIG. 8 is a diagram depicting another exemplary embodiment of a
heat assisted magnetic recording transducer.
FIG. 9 is a diagram depicting another exemplary embodiment of a
heat assisted magnetic recording transducer.
FIG. 10 is a flow chart depicting another exemplary embodiment of a
method for fabricating a waveguide in magnetic recording
transducer.
FIGS. 11-22 are diagrams depicting exemplary embodiments heat
assisted magnetic recording transducers during fabrication.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 4 is a flow chart depicting an exemplary embodiment of a
method 100 for fabricating waveguides in heat assisted magnetic
recording (HAMR) transducers. In particular, the method 100 may be
used in fabricating an interferometric tapered waveguide (ITWG).
For simplicity, some steps may be omitted, performed in another
order, interleaved with other steps and/or combined. The magnetic
recording transducer being fabricated may be part of a merged head
that also includes a read head (not shown) and resides on a slider
(not shown) in a disk drive. The method 100 is described in the
context of forming a single transducer. However, the method 100 may
be used to fabricate multiple transducers at substantially the same
time. The method 100 and system are also described in the context
of particular layers. However, in some embodiments, such layers may
include multiple sub-layers.
The method 100 also may commence after formation of other portions
of the magnetic recording transducer. For example, the method 100
may start after portions of the pole, a read transducer (if any)
and/or other structures have been fabricated. Further, formation of
other portions of the HAMR transducer may be interleaved with the
method 100. The method 100 starts after the layers for the ITWG
have been provided. For example, at least a first (e.g. bottom)
cladding layer, at least one core layer, and at least a second
(e.g. top) cladding layer are deposited. The top and/or bottom
cladding layers may, for example, include aluminum oxide and/or
silicon dioxide. In some embodiments, the top and bottom cladding
layers consist of aluminum oxide. The indices of refraction of the
top and bottom cladding layers are generally lower than the index
of refraction of the core layer.
The ITWG is defined from the waveguide layers, via step 102.
Defining the ITWG in step 102 includes defining the arms for the
ITWG. The arms of the ITWG are designed based upon a target phase
difference. More specifically, the optical lengths of the arms of
the ITWG differ to provide the target phase difference between
light traveling through the arms and meeting at the NFT. For an
ITWG having a Y-splitter, step 102 includes defining the arms to
form the Y-splitter. In embodiments including an MMI instead of a
Y-splitter, step 102 also includes fabricating the MMI. Step 102
generally includes providing a mask covering the arms of the
waveguide and etching through the at least some of layers for the
waveguide. In addition, a refill step may also be performed. This
refill step deposits a dielectric in the regions which were etched
through. In some embodiments, the dielectric deposited is the same
as the top cladding. Thus, the top cladding may be considered to
contact the bottom cladding in the regions surrounding and between
the arms of the ITWG.
As discussed above, the waveguide layers defined in step 102
include cladding and core layers. The core layer(s) include one or
more energy sensitive core layers. An energy sensitive core layer
has an index of refraction that varies in response to exposure to
energy having a particular wavelength range. For example, in some
embodiments, the energy sensitive core layer may include
Ta.sub.2O.sub.5. In some embodiments, the energy sensitive core
layer consists of Ta.sub.2O.sub.5. Ta.sub.2O.sub.5 is sensitive to
light energy in the mid and deep ultraviolet range. Thus, an energy
sensitive Ta.sub.2O.sub.5 layer has an index of refraction that
varies in response to the application of light in the mid to deep
ultraviolet range. However, the laser that is used in conjunction
with the HAMR transducer provides light in another wavelength
range. Consequently, operation of the HAMR transducer does not
change the index of refraction of the energy sensitive core layer.
For example, in some embodiments, the laser used with the HAMR disk
drive provides light in the visible range. In other embodiments, an
infrared or other laser light might be used. The wavelength range
of the laser is desired not to overlap with the wavelength range to
which the energy sensitive core layer is responsive.
After the ITWG is defined, the phase difference(s) between the arms
of the ITWG is determined, via step 104. Step 104 may be performed
at wafer level. At the wafer level, the phase differences within
the wafer may be assumed to be the same. Thus, step 104 may
determine wafer-to-wafer variations (sigma) in the phase difference
between arms of the ITWG. Within wafer variations in the phase
difference may also be determined. In some embodiments,
discrepancies between flash fields on the wafer may be ascertained.
For example, one or more test devices may be provided on each flash
field of the wafer to determine the phase differences of the ITWG
at various portions of the wafer. In some embodiments, data from
the test devices may be extrapolated to provide determinations of
the phase difference(s) in the arms of ITWGs on the wafer. However,
in other embodiments, device(s) may be individually tested. In some
embodiments, both within wafer sigma and wafer-to-wafer variations
in the phase difference between the arms may be determined.
Further, this determination may be made after the transducers have
been diced into rpw bars. Thus, determinations may be made on a row
bar-by-row bar basis. Thus, using step 104, variations between the
actual phase difference(s) of fabricated ITWGs and the target phase
difference(s) may be determined.
At least one of the arms of the ITWG is exposed to the energy that
changes the index of refraction of the energy sensitive core layer,
via step 106. In some embodiments, step 106 is also performed by
providing a mask that is opaque to the energy to which the core
layer is sensitive. For example, for some embodiments, Au, Cr
and/or other metals that block light may be used for the mask. The
mask also includes one or more apertures that leave a portion of
one or more of the arms uncovered. In some embodiments, the mask
covers all of the ITWG except for part of one arm. Such a mask can
be incorporated into fabrication of the HAMR transducer. In some
embodiments, an excimer laser, for example with a 193 nm or 248 nm
wavelength, may be used to provide the energy to which the ITWG is
exposed. Such an excimer laser may be employed because the output
beam profile may be shaped and homogenized using high grade
ultraviolet optics. Thus, a high intensity output (e.g. at least
500 mJ/cm.sup.2) may be obtained for exposing a portion of an arm
of the ITWG. In step 106, therefore, the excimer laser may simply
be scanned across the wafer, while the mask prevents energy from
the laser from reaching some portions of the ITWG and allows the
energy from the laser to reach other portions of the ITWG. In other
embodiments, row bars may be exposed to energy from the excimer
laser.
One or more of the cladding layers is desired to be substantially
transparent to the energy used in changing the index of refraction
of the energy sensitive core layer. Thus, the energy to which the
ITWG is exposed in step 106 is transmitted through the cladding
layer(s) to the energy sensitive core layer in the arm(s). The
index of refraction of the energy sensitive core layer in the
arm(s) is thereby changed in step 106. The dosage of energy used in
step 106 depends upon the phase difference determined in step 104.
The further away the phase difference is from the target phase
difference, the higher the dosage and the more the index of
refraction of the core layer may be changed.
Exposure of the arm(s) of the ITWG to the energy in step 106
changes the index of refraction in the arm(s) and alters the
optical path for the arm(s). A reduction in the index of refraction
shortens the optical path of the arm, while an increase in the
index of refraction lengthens the optical path of the arm. Because
the optical path changes through step 106, the phase difference(s)
between the arms changes. In some embodiments, a portion of only
one arm of the ITWG is exposed to the energy in step 106. The
change in the index of refraction of a portion of the arm
translates to a change in the optical path for that arm. The
optical path(s) for the arm(s) that are covered remain unchanged.
Thus, the phase difference between arms may be increased or
decreased. Fabrication of the ITWG may then be completed.
In some embodiments, the phase difference between the arms may be
altered to be closer to the target phase difference. For example,
if a material such as Ta.sub.2O.sub.5 is used for the energy
sensitive core layer, the index of refraction of the energy
sensitive core is reduced by exposure to the energy. One arm may be
designed with an optical path that is longer than what would be the
target optical path for that arm. As a result, a lag between the
light in that arm and light in the remaining arm(s) may be greater
than the target. Thus, the arms may have a phase difference that is
higher than the target phase difference, even with processing
variations. The arm having the longer optical path may be exposed
to the energy in step 106, reducing the index of refraction of a
portion of the arm. The phase difference may thus be lowered. In
some embodiments, the phase difference may be reduced to be at or
near the target phase difference. If the index of refraction of the
energy sensitive core layer increases upon exposure to the energy,
then the optical path length of one arm may be designed to have an
optical length that is shorter than a target optical length would
be. Exposing a portion of that arm what would increase the index of
refraction of that arm and, therefore, increase the optical path
length. Again, the phase difference would be altered to be closer
to the target phase difference
FIG. 5 is a diagram depicting a portion of an HAMR disk drive 120
fabricated using the method 100. For clarity, FIG. 5 is not to
scale. For simplicity not all portions of the HAMR disk drive 100
are shown. In addition, although the disk drive 100 is depicted in
the context of particular components other and/or different
components may be used. Further, the arrangement of components may
vary in different embodiments. The HAMR disk drive 120 includes a
slider 140, a laser/light source 124, media 122, and a HAMR head
130. In some embodiments, the laser 124 is a laser diode. The laser
124 is used in operation of the HAMR disk drive 120, not in the
method 100. Although shown as mounted on the slider 140, the laser
124 may be coupled with the slider 140 in another fashion. For
example, the laser 124 might be mounted on a suspension (not shown
in FIG. 5) to which the slider 140 is also attached. The laser 124
may also be oriented differently and/or optically coupled with the
HAMR transducer 150 in another manner. The media 122 may include
multiple layers, which are not shown in FIG. 2 for simplicity.
The HAMR head 130 includes an HAMR transducer 150. The HAMR head
130 may also include a read transducer (not shown in FIG. 5). The
read transducer may be included if the HAMR head 130 is a merged
head. The HAMR transducer 150 includes an NFT 151 and at least one
waveguide 160. The HAMR transducer 150 also typically includes a
pole, shield(s), coil(s) and other components for magnetically
writing to the media 122. The waveguide 160 is an ITWG manufactured
using the method 100.
FIGS. 6-7 are diagrams depicting top and side views of an exemplary
embodiment of a portion of a HAMR transducer 150 having a structure
formed using the method 100. For clarity, FIGS. 6-7 are not to
scale. The HAMR transducer 150 may be part of a merged head that
includes at least one read transducer (not shown) in addition to
one or more magnetic transducer(s) 150. Referring to FIGS. 5-7, the
ITWG 160 and NFT 151 are shown. The ITWG 160 includes arms 162 and
164 as well as a tapered region 166. The arms 162 and 164 of the
ITWG have a different optical path length. Thus, the light arriving
at the NFT 151 from the arms 162 and 164 may have a phase
difference. The ITWG is also made up of multiple layers 152, 154
and 156/158. More specifically, the ITWG includes a bottom cladding
layer 152, the energy sensitive core layer 154 and a top cladding
layer 156. The layers 152, 154 and 156 are deposited first, and
then the ITWG 160 defined. The layer 158 may be provided during the
refill portion of step 102. Because they may be made of the same
material, the layers 156 and 158 may be considered the top
cladding.
As can be seen in FIG. 6, a length, l, of the arm 164 has been
exposed to energy that changes the index of refraction of the
energy sensitive core. Thus, the portion 165 of the arm 164 has a
different index of refraction than at least part of the remaining
portion of the arm 164. In some embodiments, the region 165 has a
different index of refraction than all of the remaining portions of
the ITWG 160. For a Ta.sub.2O.sub.5 energy sensitive core layer
154, the region 165 may have a lower index of refraction than the
Ta.sub.2O.sub.5 outside of the region 165. In other embodiments,
the region 165 may have a higher index of refraction than other
portions of the energy sensitive core layers 154.
Using the method 100, the ITWG 160 has been fabricated. The phase
difference in light arriving at the NFT 151 from the arms 162 and
164 can be determined and compared to a target phase difference.
The phase difference may also be changed and corrected by changing
the index of refraction of the energy sensitive core layer 154. As
a result, the phase difference between the arms 162 and 164 may be
closer to the desired, target phase difference. This change in
phase difference may account for variations in fabrication of the
ITWG 150 including variations in the index of refraction,
thickness, and length of the arms 162 and 164, variations in the
wavelength of light produced by the laser 124 and/or other
variations in the disk drive 120. More specifically, the index of
refraction change in the region 165 is may be desired to be
sufficiently large to account for all variations in the phase
difference due to fabrication of the HAMR transducer 150. As a
result, the optical properties of light provided to the NFT 151 may
be at or closer to those desired. Consequently, performance of the
NFT 151, and thus the HAMR transducer 150, may be improved.
FIG. 8 is a diagram depicting a top view of an exemplary embodiment
of a portion of a HAMR transducer 150' having an ITWG 160' formed
using the method 100. For clarity, FIG. 8 is not to scale. Portions
of the HAMR transducer 150' are analogous to the HAMR transducer
150 and thus are labeled similarly. The HAMR transducer 150' thus
includes an NFT 151' and an ITWG 160' having arms 162' and 164'
that are analogous to the NFT 151 and the ITWG 160 having arms 162
and 164. The ITWG 160' also includes waveguide layers analogous to
layers 152, 154, 156 and 158, of which only part of the top
cladding layer 158' is shown in FIG. 8.
The ITWG 160' also includes an MMI device 168 in place of the
Y-splitter shown in the ITWG 160 of FIG. 6. In other embodiments,
the ITWG 160' may use a Y-splitter. The arm 162' also includes a
grating 170 that is incorporated into the optical path of the arm
162'. Thus, the grating 170 changes the optical path length of the
arm 162'.
In the embodiment shown, the length I' of the arm 162' has been
exposed to the energy that changes the index of refraction of the
energy sensitive core layer. As a result, the region 165' may have
a different index of refraction than other portions of the ITWG
160'. In some embodiments, the index of refraction of the region
165' is lower than some or all of the remaining portions of the
ITWG 160'. In other embodiments, the index of refraction of the
region 165' is greater than some or all of the remaining portions
of the ITWG 160'. The optical path length of the arm 162' has thus
been changed using the method 100. In the embodiment shown in FIG.
8, the region 165' includes the grating 170. Thus, the index of
refraction of portions of the grating 165' and the optical path
length for the grating 165' have been changed. In other
embodiments, the region 165' may not include the grating 170'
and/or may be part of another portion of the ITWG 160', such as the
arm 164'.
Using the method 100, the ITWG 160' has been fabricated. The phase
difference in light arriving at the NFT 151' from the arms 162' and
164' can be determined and compared to a target phase difference.
The phase difference may also be changed and corrected by changing
the index of refraction of the energy sensitive core layer 154'. As
a result, the phase difference between the arms 162' and 164' may
be closer to the desired, target phase difference. This phase
difference change due to the change in the index of refraction of
the region 165' may account for all processing variations in the
phase difference. As a result, the optical properties of light
provided to the NFT 151' may be at or closer to those desired.
Consequently, performance of the NFT 151' and the HAMR transducer
150' may be improved.
FIG. 9 is a diagram depicting a top view of an exemplary embodiment
of a portion of a HAMR transducer 150' having an ITWG 160' formed
using the method 100. For clarity, FIG. 9 is not to scale. Portions
of the HAMR transducer 150'' are analogous to the HAMR transducers
150 and 150' and thus are labeled similarly. The HAMR transducer
150'' thus includes an NFT 151'' and an ITWG 160'' having arms
162'' and 164'' that are analogous to the NFT 151/151' and the ITWG
160/160' having arms 162/162' and 164/164'. The ITWG 160'' also
includes waveguide layers analogous to layers 152, 154, 156 and
158, of which only part of the top cladding layer 158'' is shown in
FIG. 9. The ITWG 160'' is shown as including an MMI device 168' in
place of the Y-splitter shown in the ITWG 160 of FIG. 6. In other
embodiments, the ITWG 160'' may use a Y-splitter. The arm 162''
also includes a grating 170' that is analogous to the grating 170.
However in other embodiments, the grating 170' could be on the arm
164'' or omitted.
In addition, the ITWG 160'' includes a trench that is incorporated
into the optical path of the arm 164''. The trench 172 changes the
optical path length of the arm 164''. In some respects, therefore,
the trench 172 functions in an analogous manner to the grating
170.
In the embodiment shown, the length I'' of the arm 162'' has been
exposed to the energy that changes the index of refraction of the
energy sensitive core layer. Similarly, the length I''' of the arm
164'' has been exposed to the energy that changes the index of
refraction of the energy sensitive core layer. In the embodiment
shown in FIG. 9, therefore, both arms 162'' and 164'' have regions
that are exposed to the energy that changes the index of refraction
of the core. However, in other embodiments, the region 165'' or
165''' may be omitted. In addition, in the embodiment shown in FIG.
9, the regions 165'' and 165''' include the grating 170' and the
trench 172. However, in other embodiments, the regions 165'' and/or
165''' may not include the grating 170' and trench 172. As a
result, the regions 165'' and 165''' each may have a different
index of refraction than other portions of the ITWG 160''. In some
embodiments, the index of refraction of the regions 165'' and
165''' are lower than some or all of the remaining portions of the
ITWG 160''. In other embodiments, the indices of refraction of the
regions 165'' and 165''' are greater than some or all of the
remaining portions of the ITWG 160''. In some embodiments, for
example in which the energy sensitive core layer has an index of
refraction that may increase or decrease depending upon the energy
used or in which different core materials are used, the index of
refraction of one region 165'' may change in a different manner
than the index of refraction of the other region 165'''. For
example, the index of refraction of the region 165'' may increase
while the index of refraction of the region 165''' may decrease or
vice versa. The magnitude of the change of the index of refraction
of one region 165'' may be different than the magnitude of the
change of the index of refraction of the other region 165'''. For
example, the reduction in the index of refraction of the region
165'' may be greater than the reduction in the index of refraction
of the region 165'''. This may occur where one region 165''
receives a greater dose of the energy than the other region 165'''.
The optical path length(s) of the arm(s) 162'' and/or 164'' My thus
be changed using the method 100.
The ITWG 160'' has been fabricated using the method 100. The phase
difference in light arriving at the NFT 151'' from the arms 162''
and 164'' can be determined and compared to a target phase
difference. The phase difference may also be changed and corrected
by changing the index of refraction of the energy sensitive core
layer 154''. This phase difference change due to the change in the
index of refraction of the region 165'' and/or 165''' may account
for all processing variations in the phase difference between the
arms 162'' and 164''. The phase difference between the arms 162''
and 164'' may be closer to the desired, target phase difference at
the NFT 151''. As a result, the optical properties of light
provided to the NFT 151'' may be at or closer to those desired.
Consequently, performance of the NFT 151'' and the HAMR transducer
150' may be improved.
FIG. 10 is a flow chart depicting another exemplary embodiment of a
method 200 for fabricating an ITWG in an HAMR transducer. For
simplicity, some steps may be omitted. FIGS. 11-22 are diagrams
depicting side and plan views of an exemplary embodiment of a
portion of a transducer 250 during fabrication. For clarity, FIGS.
11-22 are not to scale. Referring to FIGS. 10-22, the method 200 is
described in the context of the transducer 250. However, the method
200 may be used to form another device (not shown). The transducer
250 being fabricated may be part of a merged head that also
includes a read head (not shown in FIGS. 11-22) and resides on a
slider (not shown) in a disk drive. The method 200 also may
commence after formation of other portions of the transducer 250.
The method 200 is also described in the context of providing an
ITWG having two arms in a single transducer 250. However, the
method 200 may be used to fabricate multiple ITWGs, another number
of arms and/or multiple transducers at substantially the same time.
The method 200 and device 250 are also described in the context of
particular layers. However, in some embodiments, such layers may
include multiple sublayers. The method 200 also commences after
formation of other portions of the magnetic recording transducer.
For example, the method 200 may start after the portions of the
pole, the read transducer and/or other structures have been
provided.
A first cladding layer is deposited, via step 202. In some
embodiments, the first cladding layer is an aluminum oxide layer
and may be deposited using PVD. However, in other embodiments,
additional and/or other materials including but not limited to
SiO.sub.2 might be used.
An energy sensitive core layer is deposited on the bottom cladding
layer, via step 204. The energy sensitive core layer has an index
of refraction that changes in response to exposure to energy having
a particular wavelength range. In some embodiments, the energy
sensitive core layer is Ta.sub.2O.sub.5 and may be deposited using
PVD. In other embodiments, however, additional or other materials
may be used.
A second cladding layer is deposited, via step 206. In some
embodiments, the second cladding layer is an aluminum oxide layer
and may be deposited using PVD. However, other and/or additional
materials may be used. The second, or top, cladding layer is
desired to be transparent or translucent to the wavelength range to
which the energy sensitive core layer is responsive. Aluminum oxide
is transparent to light in the mid to deep ultraviolet range to
which Ta.sub.2O.sub.5 is sensitive. Thus, in some embodiments, at
least the second (top) cladding layer is desired to consist of
aluminum oxide. The first (bottom) cladding layer may thus also be
desired to consist of aluminum oxide.
Portions of at least the energy sensitive core and second cladding
layers are removed to define the ITWG including the arms of the
ITWG, via step 208. In addition, a refill step and planarization
may also be performed as part of step 208. In general, a portion of
the first cladding layer is also removed by over-etching in order
to ensure that all of the energy sensitive core material in the
desired region is removed. FIGS. 11 and 12 depict side and top
views, respectively, of the transducer 250 during step 208. Thus,
bottom cladding layer 252, energy sensitive core layer 254 and top
cladding layer 256 have been deposited. In addition, a mask 258
having apertures 259 has been formed. The mask 258 covers the
portion of the layers 252, 254 and 256 that will form the ITWG. The
apertures 259 correspond to portions of the layers 252, 254 and 256
that will be removed in step 208. FIGS. 13 and 14 depict side and
top views, respectively, of the transducer 250 after portions of
the energy sensitive core layer 254 and second cladding layer 256
have been removed. Remaining portions of the layers 252', 254' and
256' form the ITWG 260 including the arms 262 and 264. The energy
sensitive core 254' under mask 258' corresponds to the two arms 262
and 264 of the ITWG 260 being formed. In addition, the arms 262 and
264 are configured to have different optical lengths. For example,
the physical length, width and/or thickness of the energy sensitive
core layer 254' differs for the arms 262 and 264. In the embodiment
shown, the ITWG 260 has a Y-splitter and no trenches, gratings
and/or other structures therein. However, in other embodiments,
other devices including but not limited to an MMI, one or more
trenches and one or more gratings may be provided as part of steps
202, 204, 206 and 208. FIGS. 15 and 16 depict side and top views,
respectively, of the transducer 250 after step 208 has been
completed. Thus, the cladding 270 has been deposited. The cladding
270 may be formed of the same material as the second (top) cladding
layer 256' to allow for the energy to which the energy sensitive
core layer 256' is responsive to be transmitted by the cladding
layer 270. Thus, the cladding 256' and 270 might be considered to
be the top/second cladding layer for the waveguide 260.
The arm 262 and/or 264 may be designed to have a different optical
path length(s) than would be used for the target phase difference.
For example, suppose the phase difference between the arms is
desired to be within a target phase difference range. If the index
of refraction of the energy sensitive core layer 254' can be
reduced upon exposure to a particular energy range, then the arms
262 and/or 264 may be designed such that even with processing and
other variations, the actual phase difference between the arms 262
and 264 is greater than or equal to the smallest angle in the
target phase difference range. If the actual phase difference is
outside of the target phase difference range or simply higher than
desired, then the index of refraction of the arms 262 and/or 264
may be adjusted. Thus, the actual phase difference may be brought
within the desired target phase difference range. Similarly, if the
index of refraction of the energy sensitive core layer 254' can be
increased upon exposure to a particular energy range, then the arms
262 and/or 264 may be designed such that even with processing and
other variations, the actual phase difference between the arms 262
and 264 is less than or equal to the largest angle in the target
phase difference range. If the actual phase difference is outside
of the target phase difference range or simply lower than desired,
then the index of refraction of the arms 262 and/or 264 may be
adjusted. Thus, the actual phase difference may be brought within
the desired target phase difference range.
A mask is provided on the ITWG 260, via step 210. More
specifically, the mask covers at least part of the arms 262 and
264. The mask is opaque to the energy to which the energy sensitive
core layer 254' is sensitive and includes an aperture therein. An
overcoat layer is also provided, via step 212. In some embodiments,
the overcoat layer is transparent to the energy to which the energy
sensitive core layer 254' is responsive. In some embodiments, step
210 is performed before step 212. In other embodiments, step 212 is
performed before step 212.
FIGS. 17-18 depict side and plan views of the transducer 250 after
step 210 has been performed and for an embodiment in which step 212
is performed after step 210. Thus, the mask 272 is shown. The mask
272 includes an aperture 274. The portions of the ITWG 260 under
the mask 272 are shown as a dashed line in FIG. 18. However, the
portion of the arm 262 exposed by the aperture 274 is shown as a
solid line. In the embodiment shown, only one aperture 274 exposing
a part of one arm 264 is used. In another embodiment, another
number of apertures, including one or more on the other arm 262 may
be utilized. FIGS. 19 and 20 depict side and plan views of the
transducer 250 after step 212 has been performed. Thus, an overcoat
layer 276 is provided on the mask 272. FIGS. 21 and 22 depict side
and plan views, respectively, of the transducer 250' in which step
210 is performed after step 212. Thus, the mask 272' resides on the
overcoat layer 276'. The remaining components 252', 254', 256',
260, 262, 264 and 270 may remain substantially the same. In this
embodiment, the mask 272' may be provided at the same time as pads
278. Thus, fabrication of the ITWG 260' may be simplified. Instead
of utilizing a new mask for the mask 272, the mask for the pads 278
may be changed to incorporated the mask 272' having aperture
274'.
The phase difference between the arms 262 and 264 is determined,
via step 214. Step 214 is analogous to step 104 of the method 100
and may be performed in a similar manner. Thus, the determination
of the phase difference in step 214 may be performed at the wafer
level, at the flash field level, and/or at the device level. In
addition, the actual phase difference between the arms 262 and 264
may be compared with the target phase difference. As a result,
variations of the phase difference between wafers and within wafer
may be determined.
The portion of the arm uncovered by the aperture 274/274' is
exposed to the energy to which the energy sensitive core layer 254'
is responsive, via step 216. Thus, the index of refraction of the
energy sensitive core layer 254' under the aperture 274/274' is
changed. In embodiments in which Ta.sub.2O.sub.5 is used as the
energy sensitive core layer 254', the index of refraction of the
arm 264 may be reduced. The optical path length for the arm 264 is,
therefore, changed. Consequently, the phase difference between the
arm 264 and the arm 262 is changed. Fabrication of the HAMR
transducer 250 may then be completed, via step 218.
Using the method 200, the ITWG 260 has been formed. Further,
processing and other variations in the phase difference may be
accounted for using the method 200. For example, in embodiments in
which Ta.sub.2O.sub.5 is used for the energy sensitive core layer
254', the arm 264 may be designed to have a longer optical path
length than would be used for the target phase difference. Suppose,
for example, the target phase difference is
180.degree..+-.20.degree. for light from the arms 262 and 264
meeting at the NFT (not shown). The variation in the phase
difference may be .+-.30.degree. due to variations in the
processing that result in deviations of the optical path lengths
and/or other variations such as the laser light wavelength (not
shown). In such an embodiment, the arm 264 may be designed to have
a longer optical path length such that the designed phase
difference is 195.degree.. Given the sigma in the phase difference
due to variations in processing, the actual phase difference
between the arms 262 and 264 is 165.degree.-225.degree.. At the
lower end of this range, the actual phase difference between the
arms 262 and 264 is within the target range of
160.degree.-200.degree.. However, at the higher portions of the
range of the actual phase difference)(200.degree.-225.degree. is
outside of the target range. Thus, the portion of the arm 264
uncovered by the aperture 274/274' may be exposed to energy in the
mid to deep ultraviolet range for ITWGs 250/250' that have an
actual phase difference outside of the target range. As a result,
the index of refraction of the portion of the arm 264 under the
aperture 274/274' may be reduced to account for variations in the
HAMR transducer 250/250'. The phase difference is thus lowered. In
some embodiments, the phase difference may be brought to within the
target range of 160.degree.-200.degree. and may be brought to
substantially the target phase difference of 180.degree..
Conversely, if the index of refraction of the core layer 254' is
increased by exposure to energy, the arms 262 and 264 may be
designed to have a smaller phase difference such that the largest
phase difference (including variations) is within the target range.
Adjustments may be made for ITWGs 260 having an actual phase
difference that is lower than desired by increasing the index of
refraction of the arm 264 exposed by the aperture 274/27'. Because
the phase difference in light from the ITWG 260 may be corrected,
the ITWG 260 may exhibit improved performance. As a result, the
efficiency of the NFT (not shown) may be enhanced. Consequently,
performance of the HAMR head 250 may be improved.
* * * * *